Display devices, especially a flat panel display such as a liquid crystal display (LCD) include a thin film transistor (TFT) in each pixel to drive the display device with each pixel having a dimensional size of several microns. Moreover, a plurality of pixels is arranged in a patterned matrix such as a grid-like structured pattern. Alternative light sources for flat panel displays include light-emitting diodes (LED) and the next generation organic light-emitting diodes (OLED). Like the pixel matrix, the LEDs are arranged in a patterned matrix. The light produced by each pixel or light-emitting diode is then directed to a color filter array that includes color filter units, e.g., red, green or blue (RGB) units. Like the pixels, the color filter array is also arranged in a patterned matrix such that each pixel is generally associated with an individual color unit.
One method for producing an LCD or LED color filter array involves utilizing an ink jet system to “print” RGB color inks into the individualized color units on a glass substrate. In this method, a polymer composition, hereafter, and at times referred to as “black matrix” is deposited onto a glass sheet in liquid form, pre-baked to evaporate solvents, patterned into an array of wells separated by raised walls by partially curing with ultraviolet light through a mask, developed with an alkaline solution to create the well array pattern, and then post-baked. The pattered glass substrate is then passed under an ink jet head, and very small quantities of colored ink are placed or printed into each of the wells to form the individualized RGB color units. The raised walls surrounding each well serve to contain the color filter ink printed into that well until the ink has dried, thereby preventing intermixing of the different colored inks.
The continuing demand for high picture quality, high resolution display devices will always require a greater density of pixels for a given area as well as black matrix patterns of smaller dimensions for the color filter array. There are, however, current technical limitations as to how small one can pattern black matrix in terms of line width without having the polymer material delaminate from the glass substrate during the development process. The current industry standard of black matrix line width is approximately 5 μm to 8 μm. However, display manufacturers are forever looking to increase display resolution, and therefore, there is a continued interest and technical objective to reduce black matrix line widths to 5 μm or less.